Polymer compositions with PBSA plasticizer

ABSTRACT

A polymeric composition is disclosed which includes from about 40 to about 99 weight percent of a first polymer and from about 1 to about 60 weight percent of polybutylene(succinate-co-adipate) (“PBSA”). Preferably the first polymer is selected from the group consisting of polyvinyl chloride, polylactic acid, polyhydroxy alkanoates, and mixtures thereof. A method for making the composition is also disclosed.

FIELD

This disclosure relates to polymeric compositions. More particularly,this disclosure relates to polymeric compositions incorporating apolybutylene succinate plasticizer.

BACKGROUND

Polyvinyl chloride (“PVC”) is a polymer that is commonly used in fieldssuch as construction and commodity packaging. There are two forms ofPVC, rigid and flexible. PVC is naturally a rigid polymer, but by addingplasticizer, or combinations of plasticizers, it may advantageously bemade more flexible.

Polylactic acid (“PLA”) and polyhydroxy alkanoates (“PHAs”) areadditional polymers which are of increasing commercial importance.Advantageously, PLA and PHAs may be derived from renewable biomassresources, rather than from fossil fuels. Moreover, PLA and PHA productsare biodegradable. By themselves, however, PLA and PHAs tend to be arather rigid and brittle polymer. Consequently, it is also advantageousto modify the properties of the biopolymers with a plasticizer.

Plasticizers for such purposes are typically liquids, having relativelylow molecular weights. Typical examples of plasticizers include smallmolecules such as phthalic acid diesters. Such plasticizers areproblematic in certain aspects. First, such plasticizers tend to migrateto the surface of the polymer and bloom, where exposure to the polymermay present a health risk. This blooming tendency is believed to be due,at least in part, to the relatively low molecular weight of theplasticizer. In addition, for applications where flexible PVC is to berecycled, the polymeric material can only be reground 2 or 3 timesbefore the plasticizer is broken down enough to lose its properties.

Consequently, it would desirable if a moderate to high molecular weightmaterial could be used as a plasticizer for PVC, PLA and/or PHAs, whichwould exhibit little to no migration within the polymeric material. Itwould also be desirable to provide a flexible PVC which could berecycled multiple times before its desired properties are lost.

SUMMARY OF THE INVENTION

The above and other needs are met by a polymeric composition accordingto the current disclosure. According to one embodiment, the polymericcomposition includes from about 40 to about 99 weight percent of a firstpolymer; and from about 1 to about 60 weight percent ofpolybutylene(succinate-co-adipate) (“PBSA”).

In certain embodiments of the polymeric composition, the first polymeris preferably selected from the group consisting of polyvinyl chloride,polylactic acid, polyhydroxy alkanoates, and mixtures thereof.

In some embodiments of the polymeric composition, the PBSA preferablyhas a weight average molecular weight from about 50,000 to about200,000. More preferably, the PBSA has a weight average molecular weightfrom about 80,000 to about 120,000. Further, in certain embodiments, thePBSA preferably has a viscosity from about 15,000 to about 40,000centipoise at a temperature of about 215° C.

In some instances, the PBSA of the polymeric composition preferably hasa melting point from about 20° C. to about 75° C. More preferably, thePBSA has a melting point from about 25° C. to about 40° C.

For certain embodiments of the polymeric composition, the PBSA ispreferably made up of from about 40 to about 60 mole percent moietiesderived from 1,4-butanediol, from about 10 to about 50 mole percentmoieties derived from succinic acid, and from about 10 to about 50 molepercent moieties derived from adipic acid.

In certain embodiments of the polymeric composition, the polymericcomposition includes from about 1 to about 10 weight percent of thePBSA. More preferably, the polymeric composition includes from about 50to about 60 weight percent of the PBSA.

In some embodiments of the polymeric composition, the polymericcomposition may also include also include at least one additive selectedfrom the group consisting of fillers, pigments, stabilizers,co-stabilizers, secondary plasticizers, lubricants, impact modifiers,and viscosity reducers.

In another aspect, the present disclosure provides a method for making apolymeric composition. In one embodiment, the method includes a firststep of reacting 1,4-butanediol with succinic acid and adipic acid toform a pre-polymer. The method also includes a second step ofpolymerizing the pre-polymer in a condensation polymerization reactionto form polybutylene(succinate-co-adipate) (“PBSA”). This polymericcomposition includes from about 40 to about 99 weight percent of thefirst polymer; and from about 1 to about 60 weight percent of the PBSA.

In certain embodiments of the method, the first polymer is preferablyselected from the group consisting of polyvinyl chloride, polylacticacid, polyhydroxy alkanoates, and mixtures thereof.

In some embodiments of the method, the PBSA preferably has a weightaverage molecular weight from about 50,000 to about 200,000. Morepreferably, the PBSA has a weight average molecular weight from about80,000 to about 120,000. Further, in certain embodiments, the PBSApreferably has a viscosity from about 15,000 to about 40,000 centipoiseat a temperature of about 215° C.

In some instances, the PBSA used in the method preferably has a meltingpoint from about 20° C. to about 75° C. More preferably, the PBSA has amelting point from about 25° C. to about 40° C.

For certain embodiments of the method, the PBSA is preferably made up offrom about 40 to about 60 mole percent moieties derived from1,4-butanediol, from about 10 to about 50 mole percent moieties derivedfrom succinic acid, and from about 10 to about 50 mole percent moietiesderived from adipic acid.

In certain embodiments of the method, the polymeric composition includesfrom about 1 to about 10 weight percent of the PBSA. More preferably,the polymeric composition includes from about 50 to about 60 weightpercent of the PBSA.

In certain embodiments of the method, the polymerization of thepre-polymer to form PBSA is carried out using a metal oxide or anorganometal oxide catalyst. The metal in the metal oxide or organometaloxide catalyst is preferably selected from the group consisting oftitanium, zirconium, tin, germanium, antimony, hafnium, and bismuth. Forinstance, the polymerization reaction may be carried out using acatalyst selected from the group consisting of titanium isopropoxide,zirconium butoxide, and mixtures thereof.

DETAILED DESCRIPTION

According to the present disclosure, a polymeric composition isprovided. The polymeric composition includes a first polymer and apolybutylene(succinate-co-adipate) (“PBSA”) polymer which functions as aplasticizer. Typically, the first polymer will make up from about 40 toabout 99 weight percent of the polymer composition and the PBSA willmake up from about 1 to about 60 weight percent of the polymericcomposition.

While it is believed a variety of materials may be used as the firstpolymer, the first polymer is preferably selected from the groupconsisting of polyvinyl chloride (“PVC”), polylactic acid (“PLA”),polyhydroxy alkanoates (“PHAs”), and mixtures thereof.

The term PHAs encompasses a class of biologically derived polymers. Fromthis class of polymers, preferred PHAs for use in accordance with thepresent disclosure preferably have a first repeat unit having thestructure:

and a second repeat unit having the structure:

wherein each R is independently a C3 to C19 alkyl group, and

wherein the polymer includes from about 75 mole percent to about 99 molepercent of the first repeat unit and from about 1 mole percent to about25 mole percent of the second repeat unit. A particularly preferred PHAis hydroxybutyrate-hydroxyhexanoate copolymer.

As discussed above, PVC, PLA, and PHA polymers often benefit from theinclusion of a plasticizer additive. Conventional plasticizers, however,may be subject to problems such as blooming or to degradation of theplasticizer if the polymer composition is recycled.

To overcome these difficulties, the present disclosure provides adifferent plasticizer for use with PVC, PLA, PHAs, and/or otherpolymers. Specifically, the present disclosure provides a plasticizerwhich is a polymer made from the condensation polymerization of1,4-butanediol, succinic acid, and adipic acid. As such, the polymer maybe referred to as a polybutylene(succinate-co-adipate) polymer, or PBSA.

As compared to other more conventional plasticizers, the PBSAplasticizers of the present disclosure have average molecular weightswhich are quite high. For instance, in some embodiments of the polymericcomposition, the PBSA may have a weight average molecular weight fromabout 50,000 to about 200,000. More preferably, the PBSA has a weightaverage molecular weight from about 80,000 to about 120,000.

In addition to having a high average molecular weight, the PBSAplasticizers of the present disclosure also typically exhibit relativelyhigh viscosity values as well. For instance, the PBSA may preferablyhave a viscosity from about 15,000 to about 40,000 centipoise whenmeasured at a temperature of about 215° C.

Advantageously, the PBSA plasticizers of the present disclosure havealso been found to exhibit less migration and blooming when combinedwith the first polymer. Without being bound by theory, it is believedthat the reduction in migration and blooming may be due the highermolecular weight and/or higher viscosity of the PBSA.

It has also been found that the melting point of the PBSA plasticizercan be adjusted by varying the ratio of succinic acids to adipic acidsin the final PBSA polymer. In this regard, the inventors have found thatit is generally preferred that the finished PBSA be made up of fromabout 40 to about 60 mole percent moieties derived from 1,4-butanediol,from about 10 to about 50 mole percent moieties derived from succinicacid, and from about 10 to about 50 mole percent moieties derived fromadipic acid.

The resultant PBSA preferably has a melting point from about 20° C. toabout 75 ° C., and more preferably, the PBSA has a melting point fromabout 25° C. to about 40° C.

As discussed above, the PBSA may in general make up from about 1 toabout 60 weight percent of the polymeric composition. The exact ofamount may vary depending upon how much relative rigidity or flexibilityis desired in the final polymeric composition. For applications in whicha more rigid final polymeric composition is desired, the polymericcomposition may only include from about 1 to about 10 weight percent ofthe PBSA plasticizer. In other applications in which a more flexiblefinal polymeric composition is desired, the polymeric composition mayinclude from about 50 to about 60 weight percent of the PBSAplasticizer.

In some instance, the polymeric composition may also include one or morefurther additives. For instance, the polymeric composition may includeone or more additives selected from the group consisting of fillers,pigments, polymer stabilizers, co-stabilizers, secondary plasticizers,lubricants, impact modifiers, and viscosity reducers.

Suitable fillers and pigments include talc, calcium carbonate andtitanium dioxide. Examples of suitable polymer stabilizers includetin-based stabilizers, lead-based stabilizers, rare earth metal-basedstabilizers, and metal-free stabilizers. Examples of suitableco-stabilizers include antioxidants, epoxy compounds, polyols,perchlorates, and beta-diketones. Examples of suitable secondaryplasticizers include phthalate compounds. Examples of suitablelubricants include waxes and either saturated or unsaturated fatty acidmetal salts, typically having from about 12 to about 18 carbon atoms permolecule. Examples of suitable viscosity reducers include copolymerscontaining ethylene moieties and moieties of one or more of thefollowing co-monomers: n-butyl acrylate, carbon monoxide, vinyl acetate,methyl acrylate, and ethyl acrylate. Viscosity reducing copolymers ofthis type are available from DuPont under the trade name ELVALOY.

Particularly preferred additives which may be included in the polymericcomposition may be selected from the group consisting of polybutylenesuccinate, talc, calcium carbonate, and mixtures thereof.

The PBSA plasticizer may be prepared by first mixing 1,4-butanediol withsuccinic acid and adipic acid and reacting the mixture to form apre-polymer. This initial esterification reaction is preferably carriedout at a temperature of from about 150 to about 200° C. and for a timeperiod from about 1 to about 24 hours. The reaction is preferablycarried out in an esterification reaction equipped with a heat exchangerto re-condense vapors from the reactor. Re-condensed organic componentsmay then be returned to the reactor while re-condensed water may beremoved and collected in a separate receiver vessel. Vacuum may also beapplied to the esterification reactor.

After the initial pre-polymer is formed, the pre-polymer is furtherpolymerized in a condensation polymerization reaction to form PBSA. Thispolymerization reaction is preferably catalyzed using a catalystselected from the group consisting of titanium-containing compounds,zirconium-containing compounds, and mixtures thereof. More preferably,the catalyst is selected from the group consisting of titaniumisopropoxide, zirconium butoxide, and mixtures thereof.

The polymerization reaction may be carried out in the same reactor asthe initial esterification and is preferably carried out at atemperature of from about 180 to about 275° C. and for a time periodfrom about 1 to about 96 hours in order to provide the final PBSApolymer. Vacuum may also be applied to the reactor during thispolymerization.

As noted above, the final PBSA polymer of the present disclosure haveaverage molecular weights which are quite high, typically having aweight average molecular weight from about 50,000 to about 200,000 andmore preferably from about 80,000 to about 120,000.

Finally, the completed PBSA polymer is blended with the first polymerand any other desired additive. The mixing is generally carried outusing a high shear mixing apparatus such as a Brabender mixer or anextruder and at a temperature in which both the first polymer and thePBSA plasticizer are substantially melted. Typically, the mixing iscarried out at a temperature from about 150 to about 225° C.

Advantageously, the PBSA plasticizers of the present disclosure havealso been found to exhibit less migration and blooming than conventionalplasticizers when combined with polymers such as PVC or PLA. Withoutbeing bound by theory, it is believed that the reduction in migrationand blooming may be due the higher molecular weight and/or higherviscosity of the PBSA.

Moreover, it has also been found that when the PBSA plasticizers of thepresent disclosure are blended with PVC, a flexible PVC material isprovided which may be recycled and reused multiple times before itsdesired structural properties are lost. Again without being bound bytheory, it is believed that the PBSA plasticizers of the presentdisclosure exhibit less degradation during recycling as compared toconventional low molecular weight plasticizers, and that this in turnresults in an improvement in overall recyclability of the blendedpolymeric composition.

EXAMPLES

The following non-limiting examples illustrate various additionalaspects of the invention. Unless otherwise indicated, temperatures arein degrees Celsius and percentages are by weight based on the dry weightof the formulation.

Example 1

A 5 gallon reactor equipped with a heat exchanger was charged with1,4-butanediol (21 pounds), succinic acid (11.01 pounds), and adipicacid (20.43 pounds) and heated to 180° C. for 18 hours. During the first4 hours, the vacuum was ramped down to 300 torr, after which it wasgradually reduced to 1 torr. Water was collected in the receiver. Whenthe acid number of the pre-polymer was ≤30, 45 grams of zirconiumcatalyst was added. The reaction was continued at 205° C. and 1 torrvacuum until the desired viscosity was achieved. Poly(butylenesuccinate) (2.1 pounds) was added to the reactor and stirred undernitrogen at 205° C. for 2 hours. The product was collected as a slightlytranslucent, white solid.

Example 2

The process in Example 1 was repeated using titanium isopropoxide as thecatalyst.

The foregoing description of preferred embodiments for this inventionhave been presented for purposes of illustration and description. Theyare not intended to be exhaustive or to limit the invention to theprecise form disclosed. Obvious modifications or variations are possiblein light of the above teachings. The embodiments are chosen anddescribed in an effort to provide the best illustrations of theprinciples of the invention and its practical application, and tothereby enable one of ordinary skill in the art to utilize the inventionin various embodiments and with various modifications as are suited tothe particular use contemplated. All such modifications and variationsare within the scope of the invention as determined by the appendedclaims when interpreted in accordance with the breadth to which they arefairly, legally, and equitably entitled.

What is claimed is:
 1. A polymeric composition comprising: from about 40to about 99 weight percent of a first polymer selected from the groupconsisting of polyvinyl chloride, polylactic acid, and mixtures thereof;and from about 1 to about 60 weight percent ofpolybutylene(succinate-co-adipate) (“PBSA”).
 2. The polymericcomposition of claim 1, wherein the PBSA has a weight average molecularweight from about 50,000 to about 200,000.
 3. The polymeric compositionof claim 1, wherein the PBSA has a weight average molecular weight fromabout 80,000 to about 120,000.
 4. The polymeric composition of claim 1,wherein the PBSA has a viscosity from about 15,000 to about 40,000centipoise at a temperature of about 215° C.
 5. The polymericcomposition of claim 1, wherein the PBSA has a melting point from about20° C. to about 75° C.
 6. The polymeric composition of claim 1, whereinthe PBSA has a melting point from about 25° C. to about 40° C.
 7. Thepolymeric composition of claim 1, wherein the PBSA comprises: from about40 to about 60 mole percent moieties derived from 1,4-butanediol, fromabout 10 to about 50 mole percent moieties derived from succinic acid,and from about 10 to about 50 mole percent moieties derived from adipicacid.
 8. The polymeric composition of claim 1, wherein the compositioncomprises from about 1 to about 10 weight percent of the PBSA.
 9. Thepolymeric composition of claim 1, wherein the composition comprises fromabout 50 to about 60 weight percent of the PBSA.
 10. The polymericcomposition of claim 1, wherein the composition further comprises atleast one additive selected from the group consisting of fillers,pigments, stabilizers, co-stabilizers, secondary plasticizers,lubricants, impact modifiers, and viscosity reducers.
 11. A method formaking a polymeric composition, comprising the steps of: reacting1,4-butanediol with succinic acid and adipic acid to form a pre-polymer;polymerizing the pre-polymer in a condensation polymerization reactionto form polybutylene(succinate-co-adipate) (“PBSA”); and blending afirst polymer, selected from the group consisting of polyvinyl chloride,polylactic acid, and mixtures thereof, with the PBSA to form a polymericcomposition, wherein the polymeric composition comprises from about 40to about 99 weight percent of the first polymer; and from about 1 toabout 60 weight percent of the PBSA.
 12. The method of claim 11, whereinthe PBSA has a weight average molecular weight from about 50,000 toabout 200,000.
 13. The method of claim 11, wherein the PBSA has a weightaverage molecular weight from about 80,000 to about 120,000.
 14. Themethod of claim 11 wherein the PBSA has a viscosity from about 15,000 toabout 40,000 centipoise at a temperature of about 215° C.
 15. The methodof claim 11, wherein the PBSA has a melting point from about 20° C. toabout 75° C.
 16. The method of claim 11, wherein the PBSA has a meltingpoint from about 25° C. to about 40° C.
 17. The method of claim 11,wherein the PBSA comprises: from about 40 to about 60 mole percentmoieties derived from 1,4-butanediol, from about 10 to about 50 molepercent moieties derived from succinic acid, and from about 10 to about50 mole percent moieties derived from adipic acid.
 18. The method ofclaim 11, wherein the composition comprises from about 1 to about 10weight percent of the PBSA.
 19. The method of claim 11, wherein thecomposition comprises from about 50 to about 60 weight percent of thePBSA.
 20. The method of claim 11, wherein the polymerization of thepre-polymer to form PBSA is carried out using a metal oxide or anorganometal oxide catalyst, wherein the metal in the metal oxide ororganometal oxide catalyst is selected from the group consisting oftitanium, zirconium, tin, germanium, antimony, hafnium, and bismuth. 21.The method of claim 11, wherein the polymerization of the pre-polymer toform PBSA is carried out using a catalyst selected from the groupconsisting of titanium isopropoxide, zirconium butoxide, and mixturesthereof.